Telephone system



July 6, 1943.

L. R. WALLER TELEPHONE SYSTEM Filed July 11, 1942 lNl/ENTOR LR. WALLER 7 W? MW ATTOR/VEV Patented July 6, 1943 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM Lee R. Waller, Montreal, Quebec, Canada, as-

signor to Western Electric Company, Incorpoi rated, New York, N. Y., a corporation of'New York Application July 11,

7 Claims.

scriber on the line, the magneto is operated to generate corresponding code signals which operated the bells at all the stations and signaled the operator.

It is a feature of the present invention to provide in local battery party line telephone systems means whereby signaling may be done Without the aid of a magneto, whereby one party can call another party by operating a key in code and without causing the code signals to signal the operator at the central ofiice and whereby any party can call the operator by operating another key without ringing the bells at any stations.

This invention has been illustrated in the accompanying drawing which shows two party line subscriber stations equipped in accordance with the applicants invention, a line to a central oflice and the equipment required at an operators position in accordance with this invention.

1942, Serial No. 450,563

Referring to this drawing, each of the subscriber stations I and 2 on the party line 3 is provided with a key 4 which when operated causes the operator at the central oifice to be called and a key 5 which when operated in code causes the desired subscribers station to be called. Other- Wise the subscriber station circuits are provided with the induction coil 6, transmitter 1, receiver 8, switchhook contacts 9, bell l0 and associated condenser II, a local battery l2 and a two-way rectifier Hi the purpose of which will be described hereinafter. The line 3 terminates in the central ofilce H3 in a jack l6 and a calling lamp I! and other equipments necessary for the carrying out of the applicants invention as indicated in general with the numeral l9.

If a call is to be made from subscriberstation l to call the operator at the central office, the subscriber of this station will remove the receiver 8 from the switchhook 9 and operate the key 4. When the receiver 8 is removed from the switchhook 9, the primary winding of induction coil 5 is energized over a circuit from battery l2,

transmitter l, winding 20, switchhook contacts 9, back to battery 12. This causes the armature 22 controlled by the induction coil 6 to be attracted to close a circuit across the primary winding 20 to shunt it when thekey 4 is operated as follows: from winding 29, through the front contacts and armature 22, contacts of key 4, back to winding 29. This shunt circuit causes the armature 22 to be released to open the shunt. These operations are then repeated in the same manner as the ordinary buzzer and thereby causes an alternating current of high frequency to be generated in the secondary winding 23 of the induction coil 6 from ground through the condenser 24, secondary winding 23, switchhook contacts 9 over the ring conductor of the line 3. It should be noted that the tip conductor of the line is opened at contacts of key 4. This alternating current signal transmitted over the ring conductor is received at the central ofiice through a condenser 25, contacts of relay 2! and is rectified by the rectifier arrangement shown at 28 to cause a direct current to pass through the lower winding'of relay 29 to operate this relay. This relay in operating closes a locking circuit for itself from battery through the upper winding of this relay and its armature and front contact to ground at the contacts of jack hand also a circuit for the lighting of lamp I! from battery through this lamp and the armature and front contact of relay 29 to ground at the contacts of jack It. When the operator answers this call by inserting plug 30 in the jack IS, in the usual manner, the locking circuit for relay 29 and the circuit for lamp l6 are opened at the contacts of jack I6 so that the lamp is extinguished and the relay 29 is released. It should be understood, of course, that by this time the subscriber at station I has released key 4, as it is only required to be operated for a short time suflicient to cause the operation of relay 29.

In case the subscriber at station I desires to call station 2, for example, he will operate key 5 in the code recognized by the subscriber at station 2. It should be noted that the key 5 closes the same circuit as key 4 for the primary winding 29 of the induction coil 6 so as to induce an alternating current of high frequency in the secondary winding 23 in the same manner as previou'sly described in connection with a call to an operator. In this case, however, the alternating high frequency signals pass through the winding 23, over both the tip and ring conductors,

from the tip conductor through the switchhook contacts 9, the secondary winding 23; condenser 24, contacts of keys 4 and 5 to the ring conductor. The high frequency current signals are received at the central oflice through the condensers 26 and 32 and the rectifier 33. This produces a rectified current through the winding of relay 35 for the operation of this relay. This relay in operating closes an obvious circuit for the operation of relay 2! which in operating closes a circuit for the transmission of signals over the line from the low frequency alternating current source and ground at 36 through the impedances 31, contacts of relay 2'! over the tip and ring conductors out over the line. These low frequency ringing signals will operate the bell 39 at station 2 and also the bell H3 at station I. The particular code signaled with the key 5 by the subscriber at station I will be recognized by the subscriber at station 2 who then removes his receiver from the switchhook and answers the call. When the subscriber at station I finally releases the key 5 the induction coil will, of course, cease to produce high frequency signals and relays 35 and 21 will release to stop the transmission of ordinary low frequency ringing current from the source at 36.

When a connection through the operators position at the central office is to be discontinued the subscriber may give the operator a ring-o1f signal by operating key 4 for a short interval. The operation of this key will as hereinbefore described cause a low-frequency ringing signal from source 36 to be transmitted over the line which signal will in this case pass through the jack l3 over plug 39 to signal the operators lamp in the cord circuit in the usual manner.

The varistor element i3 at a subscribers station is provided to protect the subscriber telephone set in case the subscriber should be listening while another subscriber operates one of the signaling keys. It should be observed that the condenser 24 may be of such value as to freely pass this high frequency signaling current or voice current but will not pass the low frequency ringing current signals from the source 36 and that condensers 2G and 32 are of such capacity as to ef fectively block these low frequency ringing current signals from operating relay 35 through the rectifier 33 and that the impedances 3'! are of such value as to allow the low frequency current signals from source 35 to pass freely but will effectively block the high frequency current signals induced by the induction coil from reaching the source at 36.

stations, a central ofiice, a line extending from said stations to said central office, means at each station for producing code signals of a relatively high frequency for transmission over said line, means at the central office responsive to said high frequency code signals for producing corresponding code signals of relatively low frequency for transmission back over the line, and means at each station responsive to said low frequency code signals for calling a particular subscriber depending on the code transmitted.

2. In a signaling system, party line subscriber stations, a central ofi'ice, a line extending from said stations to said central oflice, an operators position at said central oifice, means at each station for producing code signals of a relatively high frequency for transmission over both conductors of said line and for producing a relatively high frequency signal for transmission over one conductor of said line, means at the central offic responsive to high frequency code signals transmited over both conductors of the line for producing corresponding code signals of relatively low frequency for transmission back over said line, means at each station responsive to said low frequency code signals for calling a particular subscriber depending on the code transmitted, and means at the central office responsive to the high frequency signal transmitted over one conductor of the line for signaling the operator.

3. In a signaling system, party line subscriber stations, each including an induction coil, a source of current at each station, a central office, a line extending from said stations to said central office, means at each station for closing an energizing circuit for the primary winding of the induction coil across the source of current, an armature for the primary winding attracted when the primary winding is energized, a key at each station, means including said key when actuated'and the armature when attracted for closing a shunt circuit across the primary winding to deenergize it to release the armature to open the shunt circuit thereby causing the repeated energizing and deenergizing of the primary winding as long as the key is operated, said repeated energizing and deenergizing of the primary winding causing high frequency current to be induced in the secondary winding for transmission over the line, a source of low frequency current at the central office, means at the central office responsive to said high frequency current signals for rectifying them, and means responsive to the rectified current signals for connecting said low frequency source to the line for transmission of low frequency current signals over the line and a signal device at each station responsive to said low frequency current signals.

4. In a signaling system, party line subscriber stations, a central oflice, a line extending from said stations to said central office, an induction coil at each station, normally open contacts adapted to be closed on the energization of the primary winding of said coil, a source of direct current at each station, means for connecting said source in series with said primary winding to energize it, means for connecting a shunt around said primary winding and including said contacts when closed to cause said induction coil to operate as a buzzer to generate a high frequency current in the secondary winding of said coil for transmission over said line, a low frequency source at the central oflice, means at the central ofiice responsive to said high frequency current for transmitting current from said low frequency source over the line and signals at said stations responsive to said low frequency current signals.

5. In a signaling system, party line subscriber stations, a central office, a line extending from said stations to said central office, an induction coil at each station, normally open contacts adapted to be closed on the energization of the primary Winding of said coil, a source of direct current at each station, means for connecting said source in series with said primary winding -to energize it, means for connecting a shunt at the central ofi'lce, a signal at the central office, means at the central office responsive to the high frequency current when received over both line conductors in series for transmitting current from said low frequency source back over the line for actuating the signals at said stations or responsive to the high frequency current when received over one conductor of the line only for actuating said signal at the central ofiice.

6. In a signaling system, party line subscriber stations, a central ofilce, a line connecting said stations with said central oflice, means for signaling any station from any other station including means for transmitting alternating current signals of one frequency from the calling station over the line to the central office for translating said signals into alternating current signals of another frequency at the central office for transmission back over the line, and a signal responsive means at each station responsive to the translated signals.

7. In a signaling system, party line subscriber stations, a central oilice, a line connecting said stations with said central office, means for signaling the subscriber at any station by code signals from any other station or for signaling the operator at the central office, including means for producing alternating current code signals at a calling station for transmission over both conductors of a line in series or for producing an alternating current signal over one conductor of the line, means at the central ofiice for translating the code signals received over both conductors into alternating current code signals of another frequency for transmission back over the line, a signal at each of the station responsive to said translated alternating current code signals, and a signal at the central ofilce responsive to the alternating current signal received over one conductor.

LEE R. WALLER. 

